Overview
The PCF8574 I2C Expansion Board Adapter Module is an easy-to-use I/O expander that increases the number of digital input/output pins available to your microcontroller using the standard I2C protocol. Built around the PCF8574 chip, this compact module provides 8 additional bidirectional I/O pins, making it perfect for projects where GPIO availability is limited.
Key Features
- IC Used: PCF8574 I2C I/O Expander
- 8 bidirectional digital I/O pins for inputs or outputs
- Standard 2-wire I2C interface (SDA, SCL)
- Configurable hardware addresses to add up to 8 modules on one bus (0x20 to 0x27)
- Operating voltage: 2.5V to 6V, compatible with both 3.3V and 5V systems
- Compact, breadboard-friendly design for easy integration
Technical Specifications
- Chip: PCF8574 I/O expander
- I/O Pins: 8 bidirectional TTL-compatible pins
- Interface: I2C (2-wire)
- Address Range: 0x20 to 0x27 (A0, A1, A2 pin configuration)
- Supply Voltage: 2.5 V to 6 V
- Operating Temperature: typical commercial range
- Mounting: header pins for easy connection to breadboards and perfboards
Supported Platforms and Libraries
- Arduino: use Wire.h and PCF8574 libraries for simple control
- ESP32 / ESP8266: compatible via I2C and standard Arduino libraries
- Raspberry Pi: use smbus or smbus2 in Python for I2C communication
- Other microcontrollers with I2C support can also interface with this module
Applications
This module is well suited for a wide range of projects that require additional GPIO without using many MCU pins:
- Driving LCD displays with reduced wiring
- Keypad scanning and input expansion
- Sensor arrays and multiplexed inputs
- Relay and actuator control in home automation and robotics
- Educational electronics and prototyping
How to Use
Basic wiring is simple: connect VCC to your system voltage (3.3V or 5V), GND to ground, SDA to the I2C data line, and SCL to the I2C clock line. Set the address pins A0, A1, and A2 to select the module address. Many projects will also require I2C pull-up resistors on SDA and SCL; some boards include them onboard—check the module documentation.
Example I2C Addressing
- Default base address: 0x20
- Change address by wiring A0, A1, A2 to VCC or GND to select 0x20 through 0x27
- Connect multiple PCF8574 modules on the same I2C bus for scalable expansion
Why Choose the PCF8574 I2C Expansion Board
The PCF8574 module offers a low-cost, low-pin-count solution to add many digital I/O connections using only two MCU pins. It reduces wiring complexity, is widely supported by libraries and examples, and fits easily into breadboard and embedded projects where space and pins are limited.
Compatibility and Notes
- Check whether the module has onboard pull-up resistors if your setup requires them.
- Ensure your I2C bus speed and pull-ups meet the requirements for stable communication.
- Images are for illustration purposes only.
Package Contents
- 1 x PCF8574 I2C Expansion Board Adapter Module
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